7 - The Somatic Nervous System

Question 1

what is the somatic ns?

Answer 1

• voluntary

- allow proprioception

Question 2

efferent and afferents of the somatic ns?

Answer 2

afferents
- info from body to brain

efferent
- brain to effector [skeletal muscle]

Question 3

somatic afferents/efferent neurones?

Answer 3

afferents

• body to brain
• sensory n
• pseudo-unipolar
• heavy [Aa Ab] or light [Ag] myelination or none [c]

efferents

• brain to body
• motor n
• multipolar
• cell bodies in ventral horn
• highly myelinated [Aa and Ag]

Question 4

what does the cns include?

Answer 4

crainum [brain] and spinal coloum [spinal cord]

- encased in meninges and cerebrospinal fluid

Question 5

what is the PNS?

Answer 5

• links CNS to rest of the body

Question 6

what do somatic efferents supply?

Answer 6

skeletal msucle

Question 7

what is the nerve entry point?

Answer 7

where nerve enters the muscle in the NMJ

Question 8

features of the nerve entry point?

Answer 8

• found in middle of muscle
• motor neurone entry
• arterial supply and venous drainage
• where nicotinic receptors are

Question 9

advantages of myelination?

Answer 9

• increase speef of electrical conductance
• increase velocity of axonal conductance
• remain after nerve damage and guide

Question 10

what are the membranes found in a nerve?

Answer 10

outer layer - epineurium
layer around fascicle of axons - perineurium
layer around a single axon - endoneurium

Question 11

what diseases can cause demyelination?

Answer 11

diabetes [pns]
multiple sclerosis [cns]
polyneuropathies [pns]